Complimentary metal-insulator-metal (MIM) capacitors and method of manufacture

ABSTRACT

A high density capacitor and low density capacitor simultaneously formed on a single wafer and a method of manufacture is provided. The method includes depositing a bottom plate on a dielectric material; depositing a low-k dielectric on the bottom plate; depositing a high-k dielectric on the low-k dielectric and the bottom plate; depositing a top plate on the high-k dielectric; and etching a portion of the bottom plate and the high-k dielectric to form a first metal-insulator-metal (MIM) capacitor having a dielectric stack with a first thickness and a second MIM capacitor having a dielectric stack with a second thickness different than the first thickness.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application to U.S. applicationSer. No. 12/535,769, filed on Aug. 5, 2009, the contents of which areherein incorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to complimentary metal-insulator-metal (MIM)capacitors and a method of manufacture and, more particularly, to a highdensity capacitor and low density capacitor formed simultaneously on asingle wafer and a method of manufacture.

BACKGROUND

Metal-insulator-metal (MIM) capacitors are valuable components inmemory, logic and analog circuits. For example, MIM capacitors arecritical in several mixed signal integrated circuits such as analogfrequency tuning circuits, switched capacitor circuits, filters,resonators, up-conversion and down-conversion mixers, and A/Dconverters.

MIM capacitors are developed with the highest capacitance consistentwith the operating voltage. For example, in older CMOS/SiGe generations,the maximum use voltage was 6.5V which has migrated to 5V and 3.3V fornewer generations. However, as GaAs chip designs have been migratinginto SiGe and RF-CMOS, the need for both high capacitance and highoperating voltage MIM capacitors has arisen. As such, different types ofMIM capacitors may be needed for different circuit requirements. As anexample, low density (high voltage) capacitors are required for poweramplifier applications and ADC/DAC converters; whereas, high densitycapacitors are required for RF filter/coupling and decouplingcapacitors. High quality factor (Q) capacitors may also be needed for RFswitching. For this reason, there is a need to have MIM capacitors toaddress different circuit design requirements. However, there is noknown economical way to manufacture complimentary MIM capacitors on asingle chip to address different circuit design requirements.

Accordingly, there exists a need in the art to overcome the deficienciesand limitations described hereinabove.

BRIEF SUMMARY

In a first aspect of the invention, a method includes: depositing abottom plate on a dielectric material; depositing a low-k dielectric onthe bottom plate; depositing a high-k dielectric on the low-k dielectricand the bottom plate; depositing a top plate on the high-k dielectric;and etching a portion of the bottom plate and the high-k dielectric toform a first metal-insulator-metal (MIM) capacitor having a dielectricstack with a first thickness and a second MIM capacitor having adielectric stack with a second thickness different than the firstthickness.

In another aspect of the invention, a method of forming complimentarymetal-insulator-metal (MIM) capacitors comprises forming a high densitycapacitor and a low density capacitor on a same level. The high densitycapacitor and low density capacitor both have a bottom plate, a topplate and a high-k dielectric each deposited in a same processing step.

In yet another aspect of the invention, a structure comprisescomplimentary metal-insulator-metal (MIM) capacitors on a same wiringlevel on a substrate, wherein a first of the MIM capacitors comprises afirst dielectric stack having a first thickness and a second of the MIMcapacitors comprises a second dielectric stack having a second thicknessdifferent than the first thickness.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIGS. 1-8 show structures and respective processing steps in accordancewith aspects of the invention;

FIG. 9 shows a final structure and respective processing steps inaccordance with aspects of the invention; and

FIG. 10 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test.

DETAILED DESCRIPTION

The invention relates to complimentary metal-insulator-metal (MIM)capacitors and a method of manufacture and, more particularly, to a highdensity capacitor and low density capacitor simultaneously formed on asingle wafer and a method of manufacture. In embodiments, the presentinvention comprises a plurality of MIM capacitors formed on a samewiring level, e.g., a dual dielectric MIM capacitor, using a high-Kdielectric stack for a high capacitance (high density) capacitor and alow-k dielectric stack for a low capacitance (low density) capacitor.For example, in a specific embodiment, the structure includes a dualplate capacitor using the same top and bottom metal plates, where thefirst of the MIM capacitors includes a first dielectric stack having afirst thickness and a second of the MIM capacitors includes a seconddielectric stack having a second thickness different than the firstthickness. In embodiments, the first dielectric stack includes a high-kdielectric and the second dielectric stack includes a low-k dielectric.Advantageously, the MIM capacitors of the present invention can beformed with Cu or Al BEOL (back end of line) processes.

FIGS. 1-8 show structures and respective processing steps in accordancewith aspects of the invention. Specifically, FIG. 1 shows a structure 10comprising a wire 14 formed in a dielectric layer 12 using conventionaldamascene processes. In embodiments, the wire 14 is a copper or aluminumcopper wire formed using conventional lithographic, etching anddeposition processes such that no further explanation is required hereinfor those of skill in the art to understand the invention. The wire 14may be about 0.5 to 1.0 micron in height; although other dimensions arealso contemplated by the invention. The dielectric layer 12 can be anydielectric such as, for example, USG, FSG, or SiCOH.

Referring to FIG. 2, a dielectric layer 16 is formed on the structure ofFIG. 1. In particular, the dielectric layer 16 is deposited on the wire14 and the dielectric layer 12 using conventional deposition processessuch as, for example, high density plasma chemical vapor deposition(CVD) or PECVD processes. The deposition process, in embodiments, can bea two step process, depositing material such as, for example, SiN andSiO₂ or SiCN and SiO₂. In embodiments, the dielectric layer 16 can beabout 500 Å thick; although other dimensions are also contemplated bythe invention such as ranging from about 100 nm to 300 nm.

In FIG. 3, a metal plate 18 is formed on the dielectric layer 16. Inembodiments, the metal plate 18 will form a bottom plate of twocomplimentary MIM capacitors. The metal plate 18 can be deposited usingconventional sputtering techniques to a thickness of about 50 nm toabout 3000 Å; although other dimensions are also contemplated by thepresent invention. In embodiments, the metal plate 18 is a refractorymetal such as, for example, TiN, Tungsten or Tantalum or combinationssuch as, for example, TiN/W/TiN, TiN/AlCu/TiN or TaN/Ta/TiN.

As shown in FIG. 4, a low-k dielectric 20 is deposited on the metalplate 18. The low-k dielectric 20 can have a dielectric constant ofabout 10 or less. The low-k dielectric can be, for example, SiO₂ or SiN.In embodiments, the low-k dielectric 20 can be deposited using anyconventional deposition techniques such as, for example, CVD or PECVD.In one contemplated embodiment, the low-k dielectric 20 is SiO₂deposited to a thickness of about 100 nm, using low temperature methodsknown in the art (e.g., PECVD at about 350° C. or 400° C.) to achieve a100V breakdown. Those of skill in the art should appreciate, though,that the dimensions of the low-k dielectric 20 can vary such as, forexample, from about 50 nm to about 1000 nm, in certain embodiments.

In FIG. 5, portions of the low-k dielectric 20 are removed to form anisland 22. In embodiments, the portions of the low-k dielectric 20 canbe removed by a conventional lithographic and etching process. Morespecifically, in embodiments, the low-k dielectric 20 can belithographically patterned and removed to form a 2 micron wide and about50 nm to about 1000 nm high island 22. The removal process may use, forexample, a wet chemical etch, such as 100:1 DHF. In embodiments, theisland 22 (e.g., portions of the remaining low-k dielectric material) isprovided in a location where low MIM capacitance per unit area isdesired with sufficient border in areas away from the MIM top plate(e.g. about 1 um); whereas, the low-k dielectric 20 is removed where ahigh-k MIM capacitor will be formed, as discussed in more detail below.It should be understood that the low-k dielectric 20 can also be left orremoved in areas where there will be no MIM formation.

In FIG. 6, a high-k dielectric 24 is conformally deposited on thestructure of FIG. 5. In embodiments, the high-k dielectric 24 has adielectric constant greater than 20. The high-k dielectric 24 can be,for example, ZrO₂, Ta₂O₅, HfO₂, or a composite film such as any ofZrO₂/Al₂O₃/ZrO₂. The high-k dielectric 24 can have a thickness of about300 Å; although other dimensions are contemplated by the presentinvention. A metal plate 26 is then deposited on the high-k dielectric24. The metal plate 26 can be deposited using conventional sputteringtechniques. In embodiments, the metal plate 26 can have a thickness ofabout 50 nm to about 3000 Å; although other dimensions are alsocontemplated by the present invention. The metal plate 26 can be arefractory metal such as, for example, TiN, Tungsten or Tantalum orcombinations such as, for example, TiN/W/TiN, TiN/AlCu/TiN orTaN/Ta/TiN.

As seen in FIG. 7, the metal plate 26 is etched to form islands 28, 30,respectively. In this way, the metal plate 26 can be used as a top platefor a first MIM capacitor and a top plate for a second MIM capacitor. Inembodiments, the first MIM capacitor will be a high density MIMcapacitor and the second MIM capacitor will be a low density MIMcapacitor, e.g., using the low-k dielectric material.

FIG. 8 shows further processing steps to form a two plate dualdielectric material MIM capacitors, i.e., a high density MIM capacitor32 and a low density MIM capacitor 34. More specifically, the structureof FIG. 7 is selectively etched to form the high density MIM capacitor32 and the low density MIM capacitor 34. The selective etching willremove exposed portions of the high-k dielectric 24 on the metal plate18 and low-k dielectric 20, as well as provide a separation between thehigh density MIM capacitor 32 and the low density MIM capacitor 34 byetching the metal plate 18 therebetween. In this way, in embodiments,the high density MIM capacitor 32 comprises the metal plate 18, high-kdielectric 24 and top metal plate 26 (e.g., island 28). On the otherhand, the low density MIM capacitor 34 comprises the metal plate 18,low-k dielectric 20 (e.g., island 22), high-k dielectric 24, and topmetal plate 26 (island 28). Thus, a first MIM capacitor has a dielectricstack with a first thickness and a second MIM capacitor has a dielectricstack with a second thickness different than the first thickness.

FIG. 9 shows further processes steps and a final structure in accordancewith the invention. Those of skill in the art will realize, though, thatthe structure of FIG. 8 may also be considered the final structure. Inthe structure of FIG. 9, a dielectric layer 36 (e.g., ILD) can bedeposited on the structure of FIG. 8. Contacts 38 are formed in thedielectric layer 36 and in contact with the wire 24, the high densityMIM capacitor 32 and the low density MIM capacitor 34. The contacts 38can be formed using conventional lithographic, etching a depositionmethods known to those of skill in the art such that no furtherexplanation is required herein.

In one specific embodiment, the final structure includes a coplanarhigh-k dielectric MIM (high density MIM capacitor 32)and high-k andlow-k dielectric MIM (low density MIM capacitor). In one illustrativeexample, a high-k dielectric with a capacitance density of 6 fF/um² anda SiO₂ dielectric with a capacitance density of 0.7 fF/um² are used,then the final MIM capacitance density will be 6 fF/um2 for highcapacitance density MIIM (high density MIM capacitor 32) and 0.63 fF/um2for low capacitance density MIM (low density MIM capacitor 34). However,it should be understood that the above is merely one illustrativeexample that should not be considered a limiting feature. In fact, isshould be understood by those of skill in the art that specifying low-kdielectric (e.g., SiN or SiO) thickness can be specified for varyingbreakdown voltage and high-k dielectric thickness can be specified forspecific capacitance density.

FIG. 10 shows a block diagram of an exemplary design flow 900 used forexample, in semiconductor IC logic design, simulation, test, layout, andmanufacture. Design flow 900 includes processes, machines and/ormechanisms for processing design structures or devices to generatelogically or otherwise functionally equivalent representations of thedesign structures and/or devices described above and shown in FIG. 9,for example. The design structures processed and/or generated by designflow 900 may be encoded on machine-readable transmission or storagemedia to include data and/or instructions that when executed orotherwise processed on a data processing system generate a logically,structurally, mechanically, or otherwise functionally equivalentrepresentation of hardware components, circuits, devices, or systems.Machines include, but are not limited to, any machine used in an ICdesign process, such as designing, manufacturing, or simulating acircuit, component, device, or system. For example, machines mayinclude: lithography machines, machines and/or equipment for generatingmasks (e.g. e-beam writers), computers or equipment for simulatingdesign structures, any apparatus used in the manufacturing or testprocess, or any machines for programming functionally equivalentrepresentations of the design structures into any medium (e.g. a machinefor programming a programmable gate array).

Design flow 900 may vary depending on the type of representation beingdesigned. For example, a design flow 900 for building an applicationspecific IC (ASIC) may differ from a design flow 900 for designing astandard component or from a design flow 900 for instantiating thedesign into a programmable array, for example a programmable gate array(PGA) or a field programmable gate array (FPGA) offered by Altera® Inc.or Xilinx® Inc.

FIG. 10 illustrates multiple such design structures including an inputdesign structure 920 that is preferably processed by a design process910. Design structure 920 may be a logical simulation design structuregenerated and processed by design process 910 to produce a logicallyequivalent functional representation of a hardware device. Designstructure 920 may also or alternatively comprise data and/or programinstructions that when processed by design process 910, generate afunctional representation of the physical structure of a hardwaredevice. Whether representing functional and/or structural designfeatures, design structure 920 may be generated using electroniccomputer-aided design (ECAD) such as implemented by a coredeveloper/designer. When encoded on a machine-readable datatransmission, gate array, or storage medium, design structure 920 may beaccessed and processed by one or more hardware and/or software moduleswithin design process 910 to simulate or otherwise functionallyrepresent an electronic component, circuit, electronic or logic module,apparatus, device, or system such as those shown in FIG. 9, for example.As such, design structure 920 may comprise files or other datastructures including human and/or machine-readable source code, compiledstructures, and computer-executable code structures that when processedby a design or simulation data processing system, functionally simulateor otherwise represent circuits or other levels of hardware logicdesign. Such data structures may include hardware-description language(HDL) design entities or other data structures conforming to and/orcompatible with lower-level HDL design languages such as Verilog andVHDL, and/or higher level design languages such as C or C++.

Design process 910 preferably employs and incorporates hardware and/orsoftware modules for synthesizing, translating, or otherwise processinga design/simulation functional equivalent of the components, circuits,devices, or logic structures shown in FIG. 9, for example, to generate anetlist 980 which may contain design structures such as design structure920. Netlist 980 may comprise, for example, compiled or otherwiseprocessed data structures representing a list of wires, discretecomponents, logic gates, control circuits, I/O devices, models, etc.that describes the connections to other elements and circuits in anintegrated circuit design. Netlist 980 may be synthesized using aniterative process in which netlist 980 is resynthesized one or moretimes depending on design specifications and parameters for the device.As with other design structure types described herein, netlist 980 maybe recorded on a machine-readable data storage medium or programmed intoa programmable gate array. The medium may be a non-volatile storagemedium such as a magnetic or optical disk drive, a programmable gatearray, a compact flash, or other flash memory. Additionally, or in thealternative, the medium may be a system or cache memory, buffer space,or electrically or optically conductive devices and materials on whichdata packets may be transmitted and intermediately stored via theInternet, or other networking suitable means.

Design process 910 may include hardware and software modules forprocessing a variety of input data structure types including netlist980. Such data structure types may reside, for example, within libraryelements 930 and include a set of commonly used elements, circuits, anddevices, including models, layouts, and symbolic representations, for agiven manufacturing technology (e.g., different technology nodes, 32 nm,45 nm, 90 nm, etc.). The data structure types may further include designspecifications 940, characterization data 950, verification data 960,design rules 970, and test data files 985 which may include input testpatterns, output test results, and other testing information. Designprocess 910 may further include, for example, standard mechanical designprocesses such as stress analysis, thermal analysis, mechanical eventsimulation, process simulation for operations such as casting, molding,and die press forming, etc. One of ordinary skill in the art ofmechanical design can appreciate the extent of possible mechanicaldesign tools and applications used in design process 910 withoutdeviating from the scope and spirit of the invention. Design process 910may also include modules for performing standard circuit designprocesses such as timing analysis, verification, design rule checking,place and route operations, etc.

Design process 910 employs and incorporates logic and physical designtools such as HDL compilers and simulation model build tools to processdesign structure 920 together with some or all of the depictedsupporting data structures along with any additional mechanical designor data (if applicable), to generate a second design structure 990.Design structure 990 resides on a storage medium or programmable gatearray in a data format used for the exchange of data of mechanicaldevices and structures (e.g. information stored in a IGES, DXF,Parasolid XT, JT, DRG, or any other suitable format for storing orrendering such mechanical design structures). Similar to designstructure 920, design structure 990 preferably comprises one or morefiles, data structures, or other computer-encoded data or instructionsthat reside on transmission or data storage media and that whenprocessed by an ECAD system generate a logically or otherwisefunctionally equivalent form of one or more of the embodiments of theinvention shown in FIG. 9, for example. In one embodiment, designstructure 990 may comprise a compiled, executable HDL simulation modelthat functionally simulates the devices shown in FIG. 9, for example.

Design structure 990 may also employ a data format used for the exchangeof layout data of integrated circuits and/or symbolic data format (e.g.information stored in a GDSII (GDS2), GL1, OASIS, map files, or anyother suitable format for storing such design data structures). Designstructure 990 may comprise information such as, for example, symbolicdata, map files, test data files, design content files, manufacturingdata, layout parameters, wires, levels of metal, vias, shapes, data forrouting through the manufacturing line, and any other data required by amanufacturer or other designer/developer to produce a device orstructure as described above and shown in FIG. 9, for example. Designstructure 990 may then proceed to a stage 995 where, for example, designstructure 990: proceeds to tape-out, is released to manufacturing, isreleased to a mask house, is sent to another design house, is sent backto the customer, etc.

The method as described above is used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, whereapplicable, are intended to include any structure, material, or act forperforming the function in combination with other claimed elements asspecifically claimed. The description of the present invention has beenpresented for purposes of illustration and description, but is notintended to be exhaustive or limited to the invention in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art without departing from the scope and spiritof the invention. The embodiment was chosen and described in order tobest explain the principles of the invention and the practicalapplication, and to enable others of ordinary skill in the art tounderstand the invention for various embodiments with variousmodifications as are suited to the particular use contemplated.Accordingly, while the invention has been described in terms ofembodiments, those of skill in the art will recognize that the inventioncan be practiced with modifications and in the spirit and scope of theappended claims.

What is claimed:
 1. A method of forming complimentarymetal-insulator-metal (MIM) capacitors comprising forming a high densitycapacitor and a low density capacitor on a same level both having abottom plate, a top plate and a high-k dielectric, the method furthercomprising: depositing a low-k dielectric on the bottom plate; etchingthe low-k dielectric to remove it from an area of the bottom plate wherethe high density capacitor will be formed, such that the high densitycapacitor will be devoid of the low-k dielectric; and depositing ahigh-k dielectric, with a dielectric constant higher than the low-kdielectric, on the area of the bottom plate and on the low-k dielectric,such that the high-k dielectric is deposited for both the high densitycapacitor and the low density capacitor at a same time.
 2. The method ofclaim 1, wherein the bottom plate is formed on a dielectric material andthe top plate is formed on the high-k dielectric.
 3. The method of claim1, wherein the bottom plate, the top plate and the high-k dielectric areeach deposited at a same time in respective processing steps for each ofthe high density capacitor and the low density capacitor.
 4. The methodof claim 1, wherein the high density capacitor and the low densitycapacitor are formed on a same level.
 5. The method of claim 1, whereina portion of the bottom plate and the high-k dielectric are removed toseparate the high density capacitor from the low density capacitor. 6.The method of claim 1, further comprising forming a wire below the highdensity capacitor and the low density capacitor.
 7. The method of claim1, further comprising forming contacts to the high density capacitor andthe low density capacitor.